US4537489A - Automatic focusing device - Google Patents

Automatic focusing device Download PDF

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US4537489A
US4537489A US06/597,587 US59758784A US4537489A US 4537489 A US4537489 A US 4537489A US 59758784 A US59758784 A US 59758784A US 4537489 A US4537489 A US 4537489A
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signal
power supply
electromagnetic
output
projecting
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US06/597,587
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Ryoichi Suzuki
Ryuji Tokuda
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Canon Inc
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Canon Inc
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B3/00—Focusing arrangements of general interest for cameras, projectors or printers
    • G03B3/10—Power-operated focusing

Definitions

  • This invention relates to an active type automatic focusing device (hereinafter called AF device) which uses a signal projecting means such as an infrared ray emitting diode (hereinafter called IRED) and more particularly to an AF device using an electromagnetic means such as an electromagnet of the pulling-holding type for actuating the AF device to start movement of a lens barrel or the like.
  • AF device active type automatic focusing device
  • IRED infrared ray emitting diode
  • control over the actuation of an AF device such as the start of a lens barrel movement and the start of beam scanning of an IRED has been accomplished through the movement of a mechanical member which is interlocked with a shutter release button with a driving force obtained from a spring force or the like.
  • the AF device of the lens barrel and the IRED is unlocked even when the normal operations of a shutter device, a film winding device, etc. are no longer possible due to a drop in the voltage of a power source battery. Therefore, if the shutter release button is depressed under such a condition, the AF device operates resulting in abnormal operations of the shutter and the film winding device which operate subsequent to the AF device.
  • a method of accomplishing control over the actuation of the AF device by means of a magnet has been proposed.
  • the AF device is actuated by a pulling force developed by a power supply to an electromagnet and movement of the lens barrel or the like is stopped by cutting off the power supply employing this method.
  • the power supply to the magnet is inhibited by an electric circuit means so that the AF device is prevented from operating. Therefore, the problem mentioned above can be solved by this method.
  • this prior art method has a shortcoming in that: a sufficient large pulling force is required in attracting an armature for actuating the AF device with the pulling force of the electromagnet. A large pulling or attracting current of several hundred mA must flow at the time of the armature attraction. After the attraction, the armature is held at a yoke. This holding action merely requires a holding current of several ten mA. Meanwhile, however, in an AF device using an IRED, it is necessary to start a distance measuring action by lightening up the IRED upon actuation of the AF device by the pulling or attracting force of the electromagnet. In accordance with the current level of technique, a lighting current of several hundred mA is required for lighting an IRED.
  • the AF device is of the active type having a signal projecting means and is activated by a power supply to an electromagnetic means.
  • a feature of the AF device is that the power supply to the signal projecting means is inhibited while a current is flowing to the electromagnetic means avoiding overlapped loads on the power source battery, so that the above stated inconvenience can be effectively avoided giving a stable AF device operation.
  • FIG. 1 is a circuit diagram showing the electric circuit arrangement of an embodiment of the invention.
  • FIG. 2 is a timing chart showing the output wave forms of essential circuit blocks of the circuit arrangement shown in FIG. 1.
  • FIGS. 3-7 are plan views showing mechanical arrangement corresponding to the electrical circuit arrangement shown in FIG. 1.
  • FIG. 1 which shows an embodiment of the invention in a circuit diagram
  • the specification of the embodiment includes:
  • IRED infrared ray emitting diode
  • a maximum of 96 msec is the waiting time for a focus detection completion signal. Then, 16 msec after the lapse of the waiting time, the pulling or attracting action of the shutter driving magnet begins. In other words, even when the focus detection completion signal (hereinafter called an AF END signal) is produced before lapse of the waiting time, the sequence operation does not proceed to a subsequent step until termination of the waiting time. Conversely, when the AF END signal is not produced before termination of the waiting time, an AF driving magnet holding action is forcedly released for the subsequent step of operation. (It is considered abnormal to have no AF END signal 96 msec after commencement of the pulling action of the magnet for AF.)
  • the embodiment is provided with a light measuring circuit A.
  • the light measuring circuit A includes an operational amplifier 10 (hereinafter called OP amplifier) which forms a SPC head amplifier; a photogalvanic type light sensitive element 11 (hereinafter called SPC) which is connected to the two input terminals of the OP amplifier 10; and a suppressing diode 12 which is connected to the negative feedback path of the OP amplifier 10. Meanwhile, a reference voltage VREF, which is proportional to absolute temperature, is applied to the positive input terminal of the OP amplifier 10.
  • OP amplifier operational amplifier 10
  • SPC photogalvanic type light sensitive element 11
  • VREF which is proportional to absolute temperature
  • the light measuring circuit includes an expanding transister 13 which is connected to the output terminal of the OP amplifier 10; a capacitor 14 which is provided for a time constant and is connected to the transistor 13 collector; a count start switch 15 which is connected in parallel with the time constant capacitor 14 and is changed from normally closed to open in response to an opening action of the shutter; and a comparator 17 which has the positive input terminal thereof connected to the expanding transistor 13 collector and has a reference voltage V TH from a positive power source Vcc impressed on the negative input terminal thereof. Upon count completion of the time constant capacitor 14, the output terminal of the comparator 17 produces a signal AECUP.
  • a reference symbol "a” identifies an auxiliary stop; and a reference symbol “b” identifies an ND filter for obtaining information on the ASA sensitivity of the film used.
  • a circuit B indicates a known active type AF circuit using infrared rays.
  • the AF circuit B includes two-input NAND gates 31 and 32 which form an RS flip-flop circuit (hereinafter will be called RS-FF); and a three-input NAND gate 33.
  • One of the three input terminals of the NAND gate 33 receives the output of the NAND gate 31.
  • Two other input terminals of the NAND gate 33 receive a signal CLOCK and a signal AFEND which will be described hereinafter respectively.
  • Signals 10M and PUC which will be described hereinafter, are applied respectively to one of the input terminals of each of the NAND gates 31 and 32.
  • a switching transistor 34 is connected to the output terminal of the NAND gate 33.
  • Resistors, an OP amplifier 38 and transistors 35, 36, 38 and 39 form a constant voltage circuit.
  • the positive input terminal of the OP amplifier 38 is connected to a reference voltage KVC which is independent of temperature.
  • the negative input terminal of the OP amplifier 38 is connected to the voltage dividing point of the resistors 35 and 36.
  • To the emitter of the transistor 39 is connected an infrared ray emitting diode 40 (hereinafter will be called IRED).
  • the IRED 40 is arranged in combination with a light projecting lens 41.
  • a reference numeral 42 indicates an object to be photographed.
  • a light reflected by and coming from the object 42 is received by a light receiving lens 43.
  • a photogalvanic type light sensitive element 44 (hereinafter called SPC, which senses the reflection light from the object.
  • SPC 44 The output of the SPC 44 is amplified by an amplifier 45.
  • a known peak detection circuit 46 detects the peak output value of the amplifier 45.
  • a reference numeral 47 identifies a circuit for producing an in-focus signal (hereinafter called an AFEND signal). Furthermore, these circuits are arranged in the same manner as those disclosed in Japanese Patent Application Laid-Open No. Sho 56-52726 (1981).
  • An inversion circuit 48 is connected to the output terminal of the in-focus signal producing circuit 47 to produuce an AFEND signal.
  • An SW2 switch 24 closes in response to a release operation on the camera which is connected to the power source Vcc through a resistor 21.
  • NAND gates 20 and 22 form an RS-FF.
  • An inversion circuit 23 is connected to the output terminal of the NAND gate 20. Signals SW2 and SW2 are produced respectively from the output terminals of the NAND gate 20 and the inversion circuit 23.
  • reference voltage producing circuits 51 and 52 which, as mentioned in the foregoing, produce the reference voltage KVC which is temperature independent and the reference voltage VREF which is proportional to absolute temperature.
  • a numeral 53 identifies a power source battery; a switch SW1 54 closes in response to a first stroke of the camera release operation; and reference numerals 55 and 56 identify a resistor and a capacitor.
  • inversion circuits 57 and 58 To a connection point between the resistor 55 and the capacitor 56 are connected inversion circuits 57 and 58.
  • the inversion circuits 57 and 58 produce a signal PUC and a signal PUC respectively.
  • NAND gates 61 and 62 form an RS-FF.
  • a signal 10M which will be described hereinafter, is supplied as a signal 10M through an inversion circuit 64 to one of the input terminals of the NAND gate 61. Meanwhile, the signal SW2 is supplied to one of the input terminals of the NAND gate 62.
  • the reference numeral 63 identifies a two-input AND gate.
  • the signal SW2 is supplied to one of the input terminals of the AND gate 63 while the output S11 of the NAND gate 62 is supplied to the other input terminal of the AND gate 63.
  • NAND gates 65 and 66 form another RS-FF.
  • a signal 122M which will be described hereinafter, is supplied to one of the input terminals of the NAND gate 65 through an inversion circuit 68.
  • a signal 112M is supplied to one of the input terminals of the other NAND gate 66.
  • the output S21 of the NAND gate 66 and the signal 112M are supplied to the input terminals of a two-input AND gate 67.
  • the outputs S12 and S22 of the AND gates 63 and 67 are supplied to the input terminals of a two-input OR gate 69.
  • NAND gates 82 and 83 also form an RS-FF.
  • One of the input terminals of the NAND gate 82 receives the signal AFEND and a signal 96M through a NOR gate 81.
  • the signal SW2 is supplied to one of the input terminals of the other NAND gate 83.
  • the output S31 of the NAND gate 83 and the signal SW2 are supplied to the input terminals of a two-input AND gate 84.
  • NAND gates 86 and 87 form an RS-FF.
  • the signal PUC is supplied to one input terminal of the NAND gate 87 while the signal 112M is supplied to one input terminal of the NAND gate 86 through an inversion circuit 85.
  • NAND gates 89 and 90 also form an RS-FF.
  • One input terminal of the NAND gate 89 receives a signal AE CUP while the output of the NAND gate 87 is supplied to one input terminal of the other NAND gate 90 as output S43 of an inversion circuit 88.
  • the output S41 of the NAND gate 90 and the output S43 of the inversion circuit 88 are supplied to the input terminals of a two-input AND gate 91.
  • the outputs S32 and S42 of the NAND gates 84 and 91 are supplied to the input terminals of a two-input OR gate 92.
  • PULL (pulling) current driving and HOLD (holding) current driving transistors 70 and 71 are respectively connected to the output terminals of the OR gates 69 and 92.
  • the reference numeral 72 identifies a resistor for limiting the HOLD current
  • reference numeral 73 identifies the driving coil of an electromagnet
  • reference numeral 100 identifies an oscillation circuit
  • a frequency dividing circuit 101 whose frequency divides the output pulses of the oscillation circuit 100.
  • the output terminal CLOCK of the frequency dividing circuit 101 produces pulses of about 10 KHz.
  • D flip-flop circuits 102-107 (each hereinafter called D-FF) are connected, as shown in FIG. 1, to form a frequency dividing circuit.
  • the signal SW2 is supplied to the CLEAR terminals of the frequency dividing circuit 101 and the D-FFs 102-107.
  • the Q outputs 2M and 8M of the D-FFs 102 and 104 are supplied to an AND gate 108.
  • the Q outputs 16M, 32M and 64M of the D-FFs 105, 106 and 107 are supplied to an AND gate 109.
  • the Q outputs 32M and 64M of the D-FFs 106 and 107 are supplied to another AND gate 110.
  • the output of the AND gate 110 is called 96M.
  • the outputs 10M and 112M of the AND gates 108 and 109 are supplied to an AND gate 111.
  • the output of this AND gate 111 is called 122M.
  • the meaning of these signal names 10M, 122M, etc. is as follows:
  • the signals 10M, 112M, . . . respectively change to a high level 10 msec, 112 msec, . . . msec after a rise of the signal SW2.
  • the peak detection circuit 46 and the AFEND signal producing circuit 47 are set in their initial states. Under this condition (SW1 waiting condition), the output of the NAND gate 20 is at a low level. Accordingly, the signal SW2 is not produced and the signal SW2 is at a high level. Therefore, all the D-FF 102-107 are cleared. Their Q outputs thus remain at a low level. Accordingly, the outputs of the AND gates 108-111 are all at a low level. One input of each of the AND gates 63, 67 and 84 is at a low level. Their outputs and the outputs of the OR gates 69 and 92 therefore remain at a low level. The switching transistors 70 and 71 are off and no power is supplied to the coil 73 of the driving magnet.
  • the outputs S11, S21, S31 and S41 of the NAND gates 62, 66, 83 and 90 are all set at a high level.
  • the D-FFs 102-107 are released from their cleared states. Then, the output pulses of the frequency dividing circuit 101 are further divided by the D-FFs 102-107. More specifically, the Q outputs 2M-64M of these D-FFs 102-107 change respectively to a high level 2 msec, 4 mses, 8 msec, 16 msec, 32 msec and 64 msec after the signal SW2 is produced.
  • the outputs 10M, 112M, 96M and 122M of the AND gates 108-111 change respectively to a high level 10 msec, 112 msec, 96 msec and 122 msec after the signal SW2 is produced.
  • the signal 10M produced when the output 10M of the inversion circuit 64 changes to a low level, the output of the NAND gate 61 changes to a high level and the output S11 of the NAND gate 62 to a low level. Accordingly, the output S12 of the AND gate 63 also changes to a low level.
  • This turns off the driving transistor 70 cutting off the supply of a PULL current to the coil 73 of the driving magnet. In other words, the PULL current flows for a period of 10 msec. However, in the meantime, a HOLD current continues to flow.
  • the output of the NOR gate 81 changes to a low level.
  • the output of the NAND gate 82 changes to a high level and the output S31 of the NAND gate 83 to a low level. Therefore, the output S32 of the AND gate 84 changes to a low level turning off the driving transistor 71. With the transistor 71 turned off, the HOLD current supplied to the driving magnet is cut off. Then, the mechanism, which will be described hereinafter, stops the movement of the lens barrel and a distance measuring action ends.
  • the level of the output 112M of the AND gate 109 becomes high. Since the object S21 of the NAND gate 66 is set at a high level by this, the output S22 level of the AND gate 67 becomes high and the output level of the OR gate 69 also becomes high turning on the driving transistor 70. With the driving transistor 70 thus turned on, the PULL current is supplied for the second time to the driving magnet 73. The mechanism, which will be described hereinafter, then performs a shutter opening action.
  • the output 122M of the AND gate 111 changes to a high level. Accordingly, the output of the inversion circuit 68 changes to a low level and that of the NAND gate 65 to a high level respectively. Therefore, the output S21 of the NAND gate 66 and the output S22 of the AND gate 67 change to a low level turning off the driving transistor 70 and cutting off the PULL current supply. Meanwhile, when the output level of the AND gate 109 becomes high, the output of the inversion circuit 85 changes to a low level setting the outputs of the NAND gates 86 and 87 at a high level and a low level respectively. Therefore, the output S43 of the inversion circuit 88 changes to a high level.
  • the output S42 of the AND gate 91 and the output of the OR gate 92 change to a high level turning on the driving transistor 71.
  • the HOLD current continues to flow to the driving magnet 73 even fter the PULL current supply is cut off. (This also occurs in the same manner at the time of automatic focusing action.)
  • the auxiliary stop "a" closes once and then again opens.
  • the output of the OP amplifier 10 varies according to the logarithm of the quantity of light incident upon the SPC 11. A current proportional to the incident light quantity flows to the collector of the expanding transistor 13. The time constant capacitor 14 is charged with this current.
  • the output AECUP of the comparator 17 changes to a low level. Therefore, the outputs of the NAND gates 89 and 90 are respectively set at a high level and a low level.
  • the output S42 of the AND gate 91 changes to a low level.
  • the output of the OR gate 92 changes also to a low level turning off the driving transistor 71.
  • the HOLD current supply to the driving magnet then stops.
  • a known mechanism then initiates a shutter closing action.
  • two signals 96M and AFEND are supplied to the NOR gate 81. Therefore, when the signal AFEND is not produced for some reason, the HOLD current supply for autotmatic focusing is cut off without fail 96 msec after the signal SW2 is produced. Then, 112 msec after the signal SW2 is produced, the PULL current for shutter operation begins. In other words, the embodiment gives about 16 msec. of interval time after completion of an automaic focusing action and before commencement of a shutter operation, even in the worst case, so that mechanical malfunction can be precluded by this arrangement.
  • the PULL period must be set at a suitable length that is long enough to permit the magnet to perform the pulling action thereof and yet be short enough to permit distance measurement for short distances.
  • the pulling period for automatic focusing and commencement of IRED lighting are controlled by a predetermined timing.
  • the invention is not limited to such an arrangement.
  • completion of the pulling action of the magnet may be detected by suitable means and the pulling (PULL) current may be switched over to an IRED lighting current by switching means which operates in response to a detection signal produced by the pulling completion detecting means.
  • FIGS. 3-7 are plan views showing mechanical arrangements corresponding to the electrical circuit arrangements shown in FIG. 1.
  • a reference numeral 201 indicates a magnet yoke.
  • the yoke 201 is secured to a shutter base plate, which is not shown.
  • the magnet yoke 201 is provided with a magnet coil 73 which is also shown in FIG. 1 and which produces a magnetic field when a power supply is effected thereto from the power source.
  • An armature 203 is opposed to the fore end part of the yoke 201 leaving a slight gap between them. The armature 203 is pulled or attracted by and comes into contact with when a pulling current is impressed on the magnet coil 73.
  • a control lever 205 which is formed into one unified body with the armature 203 and is pivotally supported by a shaft 204 secured to the shutter base plate rotates clockwise on the shaft 204 when the armature is attracted to the yoke 201.
  • a spring 206 urges the control lever 205 in the counterclockwise direction as viewed in the drawings.
  • a driving member or driving plate 207 is slidable in the right direction as viewed in the drawings and is guided by a shaft 208 which is secured to the shutter base plate in the same manner as the shaft 204.
  • the driving plate 207 is also urged in the same direction by a spring 209 which is disposed at one end thereof.
  • the driving plate 207 is provided with a locking part 207a which engages a bent part 205a formed on one side of the armature 203 in the initial state of the device; and another locking part 207d which also engages the bent part 205a when the armature is released from a first attraction by the magnet yoke 201.
  • These locking parts 207a and 207d are adjacently disposed at the right end of the driving plate 207, as viewed in the drawings.
  • the driving plate 207 is further provided with a locking part 207b which is at the other end to engage a notched part 205b of the control lever 205 when the armature is attracted, for the first time, by the magnet yoke 201.
  • the driving plate 207 is arranged such that the pulling and releasing actions of the magnet yoke 201 cause the driving plate 207 to move in a stepwise manner to the right, as viewed in the drawings.
  • An opening lever 210 is rotatably supported by a shaft 211 which is erected on the driving plate 207.
  • a spring 212 urges the opening lever 210 to move counterclockwise, as viewed in the drawings.
  • the lever 210 is provided with a hooked end part 210a which engages a fore end part 215a of a shutter operating lever 215 when the driving plate 207, which moves stepwise, makes the last move thereof.
  • At the other end of the opening lever 210 there is erected a pin 210b which is pushed by a pushing part 205c of the control lever 205 rotating the opening lever 210 clockwise when the hooked part 201a disengages from the fore end part 215a of the lever 215.
  • a shutter blade 213 is rotatably supported by a support shaft 214 which is secured to the shutter base plate, which is not shown. There is provided another shutter blade which is symmetrically arranged with the shutter blade 213 but is omitted from the illustration for the sake of simplification. This shutter blade 213 is provided with a slot which engages a pin 216 erected on the shutter operating lever 215. The shutter blade 213 thus follows the movement of the shutter operating lever 215.
  • a spring 218 which is rotatably supported by a support shaft 217 secured to the base plate, urges the shutter operation lever 215 to move it counterclockwise.
  • a clamping lever 219 is pivotally supported by a support shaft 220, which is secured to the shutter base plate.
  • the lever 219 is urged to move counterclockwise by a spring 221.
  • the clamping lever 219 is provided with a hooked part 219a which is formed at one end of the lever 219 and engages an initial position locking part 222c of an automatic focusing control plate 222 (hereinafter called AF control plate).
  • AF control plate automatic focusing control plate
  • the AF control plate 222 is guided by pins 223 and 224 secured to the shutter base plate and is urged by a spring 225 toward the left, as viewed in the drawings.
  • a toothed part On one side of the AF control plate 222 is provided a toothed part, which engages an escape wheel 226.
  • the wheel 226 is rotatably supported by a support shaft 227 the rotation of which is restricted by an anchor 228.
  • the anchor 228 is swayingly mounted on a support shaft 229.
  • a light projecting or emitting element lever 230 is pivotally supported by a support shaft 231 secured to a camera body or the like (not shown).
  • the lever 230 is urged clockwise by a spring 232.
  • One end of the lever 230 is in contact with a cam part 222a formed on one side of the AF control plate 222 while the other end has the light emitter element IRED 40, shown in FIG. 1, secured thereto.
  • Arranged in combination with the IRED 40 are a light projecting lens 41; a light receiving lens 43; and a light sensitive element 44. These elements are secured respectively to the camera body or the like (not shown) to constitute the known mechanism of an active type automatic focus detecting device.
  • the light receiving element IRED 40 is shown in the drawing to scan from infinity to close-up, it is needless to say the element may scan from close-up to infinity.
  • FIGS. 3-7 The mechanical arrangement shown in FIGS. 3-7 operates as follows:
  • the magnetic force developed at the magnet yoke 201 causes the armature 203 to be attracted by the fore end part of the magnet yoke 201.
  • the control lever 205 which is formed into one unified body with the armature 203, rotates on the shaft 204.
  • the hooked end part 205a of the control lever 205 then disengages from the locking part 207a of the driving plate 207.
  • the urging force of the spring 209 moves the driving plate 207 to the right, as viewed in the drawings.
  • the protruding part 207c of the driving plate 207 pushes one end of the clamping lever 219 upward, as viewed in the drawing.
  • the clockwise rotation disengages the hooked part 219a of the clamping lever 219 from the locking part 222c of the AF control plate 222.
  • the urging force of the spring 225 then moves the AF control plate 222 to the left, as viewed in the drawing.
  • the movement takes place at a prescribed speed determined by the speed governing mechanism consisting of the escape wheel 226 and the anchor 228.
  • the AF control plate 222 moving in this manner, the light emitting element lever 230 is operated by the cam part 222a of the AF control plate 222. Therefore, the automatic focus detecting device performs a distance measuring action with the light emitting element or IRED 40 and the light sensitive element 44.
  • This movement of the driving plate 207 continues until the locking part 207d of the driving plate 207 comes into engagement with the hooked part 205a of the control lever 205, as shown in FIG. 5. Furthermore, the movement of the driving plate 207 disengages the clamping lever 219 from the protruding part 207c of the driving plate 207. The urging force of the spring 221 then rotates the clamping lever 219 counterclockwise. This brings the hooked part 219a of the clamping lever 219 into engagement with the claw part 222b of the AF control plate 222. This engagement then stops the leftward movement of the AF control plate 222. With the AF control plate 222 stopped, the focusing operation on the photo-taking lens 234 ends.
  • the magnet yoke 201 When a second power supply is supplied to the magnet 73, the magnet yoke 201 again pulls the armature 203. With the armature 203 pulled or attracted again, the locking part 207d of the driving plate 207 and the hooked part 205a of the control lever 205 are disengaged from each other. The urging force of the spring 209 then moves the driving plate 207 to the right, as viewed in the drawing. At this time, the hooked part 210a of the opening lever 210, which is rotatably attached to one end of the driving plate 207, is engaging the fore end part 215a of the shutter operating lever 215. Therefore, the shutter operating lever 215 rotates counterclockwise as the driving plate 207 moves, as shown in FIG. 6.
  • This rotation of the shutter operating lever 215 rotates the shutter blade 213 counterclockwise on the support shaft 214 and exposure begins accordingly.
  • the power supply to the magnet coil 73 is cut off. With the power supply cut off, the attracting force of the magnet yoke 201 on the armature disappears. Therefore, the urging force of the spring 206 rotates the control lever 205 counterclockwise, as shown in FIG. 7.
  • a pushing part 205c of the control lever 205 pushes down a pin 210b provided on the opening lever 210.
  • the hooked part 210a of the lever 210 disengages from the fore end part 215a of the shutter operating lever 215.
  • the urging force of the spring 218 rotates the shutter operating lever 215 counterclockwise.
  • the shutter blade 213 then also rotates in the return direction thereof to close the shutter.
  • the power supply to signal projecting means is inhibited during the period when power is supplied to the electromagnetic means, as described in detail in the foregoing.
  • This arrangement therefore precludes the possibility of overlapped imposition of loads on the battery, so that the automatic focusing operation can be accomplished in a stable manner.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Focusing (AREA)
  • Automatic Focus Adjustment (AREA)
US06/597,587 1981-08-21 1984-04-09 Automatic focusing device Expired - Lifetime US4537489A (en)

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JP56131080A JPS5833209A (ja) 1981-08-21 1981-08-21 自動焦点調節装置
JP56-131080 1981-08-21

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6068189A (en) * 1996-01-18 2000-05-30 Datalogic S.P.A. Focusing device including capacitive transducer position sensor

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60135712U (ja) * 1984-02-20 1985-09-09 三洋電機株式会社 自動焦点カメラ
JPS60214320A (ja) * 1984-04-11 1985-10-26 Kowa Co 自動焦点調節装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4053240A (en) * 1973-10-26 1977-10-11 Canon Kabushiki Kaisha Object distance measuring system for an optical instrument
US4199244A (en) * 1976-10-04 1980-04-22 Polaroid Corporation Automatic focusing camera
US4257705A (en) * 1978-03-23 1981-03-24 Canon Kabushiki Kaisha Device for focus detection or distance detection
US4330202A (en) * 1978-12-11 1982-05-18 Canon Kabushiki Kaisha Range detecting device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4053240A (en) * 1973-10-26 1977-10-11 Canon Kabushiki Kaisha Object distance measuring system for an optical instrument
US4199244A (en) * 1976-10-04 1980-04-22 Polaroid Corporation Automatic focusing camera
US4257705A (en) * 1978-03-23 1981-03-24 Canon Kabushiki Kaisha Device for focus detection or distance detection
US4330202A (en) * 1978-12-11 1982-05-18 Canon Kabushiki Kaisha Range detecting device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6068189A (en) * 1996-01-18 2000-05-30 Datalogic S.P.A. Focusing device including capacitive transducer position sensor

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